The present invention relates to a part which is used in semiconductor fabrication processes, and more particularly, to the use of a part having a visual indicator which identifies the end of the part""s useful life.
A semiconductor device is formed by layering various materials on a wafer in a prescribed pattern. Popular methods for depositing semiconductor layers include physical vapor deposition and chemical vapor deposition. While these processes are effective for film formation, material that deposits on surfaces within the deposition chamber other than those of the substrate may tend to flake or crumble from chamber surfaces as the chamber thermally cycles (e.g., deposition chambers are heated to temperatures typically between 150xc2x0 C. to 500xc2x0 C. during wafer processing, and allowed to cool between sequentially processed wafers), particularly when a significant amount of material has accumulated. Such flaking or crumbling may cause wafer contamination. Accordingly, in order to reduce this type of contamination, chamber surfaces must be periodically cleaned or replaced. To reduce the cost per article processed, such part replacement should be minimized and cleaning procedures simplified. One technique for simplifying chamber cleaning is to use process kits (e.g., chamber components such as shields, pedestals, shutters, collimators and clamp rings (as described below) which may be easily removed from the chamber for cleaning or replacement.
Typically, once removed from the chamber, process kit parts are cleaned via submersion in a chemical solution which etches the deposited material from the part. Additionally, some components may require bead blasting or other abrasive techniques to physically remove deposited material from the part. Both chemical and physical removal of deposited materials inevitably removes (e.g., etches or blasts away) a portion of the part""s surface. After several cleanings, a portion of the part""s surface may be removed to the extent that the part no longer falls within the range of acceptable dimensions (i.e., part tolerance) required for the part to perform its intended function (e.g., a clamp ring should uniformly press a wafer against the susceptor, an edge ring should uniformly cover a wafer""s perimeter, a collimator, shield and shutter should uniformly block deposited material from certain surfaces, etc.).
Accordingly, a part which is out of tolerance should be immediately replaced.
It is difficult to accurately determine whether a cleaned part is out of tolerance. Part tolerances are often too small to determine via visual inspection. Therefore, paradigms such as a maximum number of cleanings, followed by discarding of the part, are employed. However, as, the amount of material removed by each cleaning cycle may vary considerably, employing a recommended number of cleanings per useful life (e.g., each part may be cleaned five times) results in many parts being discarded while they are still functional. Because each part replacement increases wafer processing costs, manufacturers often resort to time consuming metrology methods such as measuring a part with calipers or other measurement tools to determine whether a part is out of tolerance. However, metrology methods are time consuming and labor intensive which makes them costly alternatives.
Accordingly, there is a need for an improved method and apparatus for determining whether a process kit part is out of tolerance.
The invention provides a process kit part that has a visual indicator formed in a surface that is to be subjected to a cleaning process. Specifically, the invention provides a recyclable process kit part made of a material, and having a first surface that has a first elevation; and a visual mark formed in the first surface, the mark extending to a second elevation, wherein the distance between the first elevation and the second elevation is adapted such that the mark is visible until an amount of the material is removed from the part so as to make the part nearly out of tolerance. The visual indicator may be a mark which extends above the main surface of the part, or a mark which extends below the main surface of the part. The structure comprising the mark is eroded during cleaning; the erosion of the mark is proportional to the erosion of the surfaces of the part which when sufficiently eroded yield an out of tolerance part.
A preferred method of using the part provides a processing chamber which contains the inventive part, and performing a process therein that results in deposition of material on the inventive part. The deposited material then is cleaned from the inventive part (such as via an etch process and/or a bead blasting process) which results in erosion of the part surfaces and the mark, and the part is determined to be within tolerance based on the mark""s visibility.
With use of the present invention a part can be quickly determined to be within tolerance, and the use of time consuming metrology methods is reduced. Moreover, when the inventive mark""s visibility is not clear, an operator is on notice that the part may be out of tolerance, and costly defects associated with out of tolerance parts may be avoided.
Other features and advantages of the present invention will become more fully apparent from the following detailed description of the preferred embodiments, the appended claims and the accompanying drawings.